Activation energy

Science

Definition

Activation energy (Ea) is the minimum amount of energy that reacting molecules must possess for a chemical reaction to occur. It represents the energy barrier that must be overcome for reactants to be converted into products.

Examples

  • Striking a match provides the activation energy needed to start combustion of the match head chemicals
  • Enzymes in your body lower the activation energy of biochemical reactions, making them occur at body temperature
  • A spark plug provides the activation energy to ignite the fuel-air mixture in a car engine
Key Fact

Arrhenius equation: k = Ae^(−Ea/RT); catalysts lower Ea without being consumed.

Related Terms

Catalysts Reaction rates Enthalpy Enzyme structure

Study This Concept

Practice activation energy with free review games in these units:

AP Chemistry Unit 5: Kinetics